title: Timing of lower extremity frontal plane motion differs between female and male athletes during a landing task.
abstract: BACKGROUND
  Female athletes are at a greater risk for noncontact anterior cruciate ligament injuries than male athletes. Gender differences in frontal plane kinematics (hip adduction, knee valgus, and ankle eversion) and temporal relationships that make up the components of dynamic knee valgus may explain this discrepancy.
  
  
  OBJECTIVE
  The authors hypothesized that women would reach peak frontal plane kinematic values earlier during landing compared with their male counterparts.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Hip, knee, and ankle 3-dimensional kinematics were measured using high-speed motion capture in 10 National Collegiate Athletic Association Division I female athletes and 10 male practice squad athletes during a drop-jump landing. Independent t tests were used to analyze each dependent variable to identify differences between genders.
  
  
  RESULTS
  Maximum hip adduction, knee valgus, and ankle eversion occurred earlier in women than in men (mean differences 33.7% of stance [95% CI, 20.2%-47.2%], 41.7% [95% CI, 31.5%-51.6%], 16.5% of stance [95% CI, 7.3%-25.6%], respectively). Maximum hip adduction and knee valgus occurred before maximum knee flexion in women and after in men (mean differences 0.11 seconds [95% CI, 0.05-0.18 seconds], 0.19 seconds [95% CI, 0.13-0.25 seconds], respectively). Maximum ankle eversion occurred earlier in women than in men (mean difference 0.06 seconds [95% CI, 0.01-0.11 seconds]). There was a significant difference between genders for angular velocity of knee valgus (mean difference = 25.53 deg/sec [95% CI, 8.30-42.77 deg/sec]).
  
  
  CONCLUSIONS
  Frontal plane kinematic temporal relationships at the hip, knee, and ankle differ between genders. The components of dynamic knee valgus peak during the deceleration phase in women and during the acceleration phase in men during a drop-jump landing. These data suggest that men and women employ a completely different kinematic landing/jumping strategy and that women land and collapse very rapidly into valgus compared with their male counterparts.
  
  
  CONCLUSIONS
  The differences in timing of the components of dynamic knee valgus between women and men may contribute to the increased risk of noncontact anterior cruciate ligament injuries in female athletes. There may be implications for neuromuscular reeducation training in those at risk for anterior cruciate ligament injury so the components of dynamic valgus occur later in the landing phase of jumping.
authors.affiliation: Human Performance Laboratory, Kinesiology Department, University of Connecticut, Storrs, Connecticut 06269, USA. mickpt@sbcglobal.net
authors.forename: Michael F
authors.initials: MF
authors.lastname: Joseph
authors.forename: Michael
authors.initials: M
authors.lastname: Rahl
authors.forename: Jessica
authors.initials: J
authors.lastname: Sheehan
authors.forename: Bradley
authors.initials: B
authors.lastname: MacDougall
authors.forename: Elaine
authors.initials: E
authors.lastname: Horn
authors.forename: Craig R
authors.initials: CR
authors.lastname: Denegar
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Trojian
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Anderson
authors.forename: William J
authors.initials: WJ
authors.lastname: Kraemer
mesh_terms: D000328:Adult; D000843:Ankle Joint / Q000502:physiology / Q000503:physiopathology*; D016118:Anterior Cruciate Ligament / Q000502:physiology / Q000503:physiopathology*; D000070598:Anterior Cruciate Ligament Injuries; D056352:Athletes; D001696:Biomechanical Phenomena; D005260:Female; D006621:Hip Joint / Q000502:physiology; D006801:Humans; D007718:Knee Injuries / Q000209:etiology*; D007719:Knee Joint / Q000502:physiology; D008297:Male; D009068:Movement / Q000502:physiology*; D012737:Sex Factors; D013997:Time Factors; D014741:Video Recording; D055815:Young Adult